Method for producing a diesel fuel

ABSTRACT

A method relating to oil refining, which can be used to produce low-sulfur diesel fuel, comprising oil demineralization and distillation, and extraction and mixing of diesel fractions, followed by hydrogen refining of the mixture. In an atmospheric tower, two diesel fractions that boil at 171-341° C. and 199-360° C. are extracted. The 199-360° C. fraction is sent for liquid extraction to purify it from benzalkylthiophens. Amide, a product of organic amine interaction with organic acid, is used as the extractant. Fractions are then mixed, maintaining the balance ratio (based on the output) of 171-341° C. and 199-360 ° C. after refining. When refined using the ASTM D-86 method, the mixture of these fractions has an end boiling point no higher than 360° C. The technical result is production of diesel fuel with a 171-360° C. fractional composition and sulfur content of no higher than 10 ppm.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a national stage application and claims the benefitof the priority filing date in PCT/RU2012/000475 referenced in WIPOPublication WO2012/177180 filed on Jun. 19, 2012. The earliest prioritydate claimed is Jun. 22, 2011.

FEDERALLY SPONSORED RESEARCH

Not Applicable

SEQUENCE LISTING OR PROGRAM

Not Applicable

BACKGROUND

The invention relates to oil refining and can be used in production oflow-sulfur diesel fuel which is being increasingly used in Russia andEurope.

The projected fuel demand in Europe (“

” [Oil and Gas Technology] magazine, No. 6, 2007, p. 94) indicatesincreasing production of diesel fuel and decreasing production ofgasoline:

2005 2010 2015 2020 Gasoline, million ton/year 137.0 128.3 127.0 131.0Diesel fuel, million ton/year 201.2 237.8 251.8 251.5

Dieselization of vehicular transport is due to the fact that a dieselengine is 25-30% more cost effective than a gasoline one.

According to technical regulations

On Fuel Requirements

(RF Government Decree No. 118 of Feb. 27, 2008), the sulfur content ofdiesel fuel produced after December 2012 shall not exceed 10 ppm.

Known is the method for production of diesel fuel (RF patent No.2247140) comprising single-stage hydrogen refining of light gas-oilfraction (end boiling point no higher than 300° C.) and two-stagehydrogen refining of heavy gas- oil fraction (initial boiling point notbelow 300° C.) using an aluminum-nickel- molybdenum ofaluminum-cobalt-molybdenum catalyst. Hydrogen refining is performed atan elevated temperature and pressure with subsequent compounding ofhydrogen-refined fractions. The sulfur content of the produced dieselfuel exceeds 10 ppm.

Also known is the method for production of low-sulfur diesel fueldescribed in the RF patent No. 2303624. According to this method, fuelis produced using two-stage catalytic hydrogen refining of the 180-360°C. diesel fraction using hydrogen-rich gas at elevated temperature andpressure wherein vapor and liquid phases of the first stage hydrogenatorare produced. The liquid phase of the first stage hydrogenator ishydrogen-refined at the second stage, producing a second- stagehydrogenator which is then combined with the vapor phase of the firststage hydrogenator. This method does not provide diesel fuel sulfurcontent lower than 10 ppm.

The disadvantage of the known methods is that they are not designed forproducing fuel with sulfur content no higher than 10 ppm.

The closest to the claimed invention in technical essence is a methodfor production of diesel fuel described in the RF patent No. 2387700;the authors have selected this method as the prototype.

According to the method described in the RF patent No. 2387700, afteroil is demineralized it is distilled. Here, diesel fraction with a171-341° C. boiling temperature is extracted from an atmospheric tower.Fractions with a boiling temperature above 341° C. together with fueloil are fed to a vacuum column for further refining. Fractions with a181-304° C. and 226-326° C. boiling temperature are extracted from avacuum column and mixed with diesel fraction from the atmospheric towerwhile maintaining a balance ratio, wherein the end boiling point (EBP)of the balanced mixture of these fractions, when refined using the ASTMD-86 method, does not exceed 340° C. The mixture is hydrogen refined,producing low-sulfur diesel fuel with a sulfur content no higher than 10ppm. The technical result is that the method per the invention makes itpossible to produce diesel fuel with a sulfur content no higher than 10ppm.

This effect is due to the fact that sulfur, which is a component ofalkylbenzothiophens (ABT) and is sterically hindered by polyaromaticrings, is removed from diesel fuel by fractionation.

Known from literature (for instance, Salvatore Torrisi, Michael Gunter,“Petroleum Technology Quartlerly” magazine, 2004, vol. 9, No. 4, pp.29-35) is that fractions with EBP above 340° C. contain sulfur compoundsof ABT where sulfur is combined with sterically hindered polyaromaticrings, and its extraction during hydrogen refining is impeded due tosterical hindering of the sulfur atom. To remove sterically hinderedsulfur, it is necessary to increase the temperature of the hydrogenrefining process, which facilitates catalyst coking and shortens theplant service cycle.

However, decreasing the diesel fraction EBP from 360° C. to 340° C.reduces potential extraction of diesel fuel.

SUMMARY

The technical result of the claimed invention is the production ofdiesel fuel with a sulfur content no higher than 10 ppm with broadfractional composition at 171-360° C.

The stated technical result is achieved using a method for production ofdiesel fuel comprising oil demineralization and distillation, andextraction of two diesel fractions with boiling temperature of 171-341°C. and 199-360° C. in an atmospheric tower. The 199-360° C. fraction issent for extraction of ABT using the liquid extraction method, followedby mixing the refined 199-360° C. fraction with the 171-341° C.fraction. Then, the fractions mixture is sent for hydrogen refining onan aluminum-cobalt-molybdenum or aluminum-nickel-molybdenum catalyst.Hydrogen refining of the fractions mixture is performed in a singlestage.

The method for production of diesel fuel proposed as the inventionsolves this problem by removing ABT using the liquid extraction method.

DESCRIPTION

The proposed method is realized as follows. Demineralized oil is fed toan atmospheric tower for distillation. In addition to gasoline andkerosene fractions, two diesel fractions with 171-341° C. and 199-360°C. boiling point are extracted. The 199-360° C. fraction is sent forremoving ABT using the liquid extraction method, followed by mixing therefined 199-360° C. fraction (raffinate) with the 171-341° C. fraction.Then, the fractions mixture is sent for hydrogen refining on analuminum- cobalt-molybdenum or aluminum-nickel-molybdenum catalyst. Whenrefined using the ASTM D-86 method, the EBP of the balanced mixture ofthese fractions (output-based mixing) is no higher than 360° C.

The process parameters of the atmospheric tower during extraction ofdiesel fractions conform to design standards:

-   tower pressure—no more than 2.5 kg/cm,-   tower top temperature—120-170° C.,-   tower bottom temperature—no more than 360° C.

Parameters of hydrogen refining of diesel fuel depends on the catalysttype and activity, the quality of feedstock and requirements to the endproduct, and is selected according to the design solution. For instance,for aluminum-cobalt-molybdenum or aluminum-nickel-molybdenum catalyst:pressure—20-60 kg/cm², temperature—340-400° C., feedstock volumetricfeed rate—1-3 hour⁻¹, hydrogen-bearing gas circulation rate—200-600nm³/m³, circulating gas hydrogen content—8595% by volume.

Reduction of sulfur in diesel fuel results in decreasing its fuellubricity. So to produce diesel fuel meeting regulatory requirements, itis necessary to introduce lubricating and depressor-dispersive additivesto meet operational specifications in terms of low-temperaturecharacteristics, detergent additives, etc.

Adding the additives does not affect the amount of sulfur in finishedfuel. The proposed method for removing ABT from diesel fuel—thefeedstock for a hydrogen refining plant—has been developed on a pilotplant using diesel fuel fractions produced in a commercial plant.

Invention Embodiments Including the Best Invention Embodiment. Resultsof the experiments that were conducted are shown in Table 1. Theydemonstrate the following.

All experiments were conducted at 40-45° C. This temperature rangeensures good mixing of diesel fuel and extractant. The temperature issufficient for reducing viscosity of initial components—the 199-360° C.diesel fraction and extractant.

The feedstock:extractant mass ratio varied from 1:1 to 1:4. At the 1:1feedstock:extractant ratio, maximum residual ABT was observed. The 1:2to 1:3 feedstock:extractant ratio was selected as the optimum ratio.Increasing the feedstock:extractant ratio to 1:4 does not result infurther decrease of ABT.

The selected optimum contact—mixing—time was 2-3 hours. However, basedon results of the ABT content analysis, one hour of mixing is not enough(experiment 1), and increasing mixing time to 4 hours does not reducethe ABT content (experiment 4).

The optimum parameters are:

-   temperature—40-45° C.,-   feedstock:extractant mass ratio—1:2 to 1:3,-   mixing time—2-3 hours

The detailed description of experiments 1-6 is provided below: ExampleNo. 1. According to the claimed method, demineralized oil is fed to anatmospheric tower for distillation.

During distillation, two diesel fractions with 171-341° C. and 199-360°C. boiling point are extracted. The 199-360° C. fraction is sent for ABTextraction using the liquid extraction method.

The product of interaction of organic amine (for instance, aniline) withorganic acid (for instance, acetic acid) is used as extractant. Theresulting acetic anilide (extractant) is a dark cherry-colored liquidwith a boiling point higher than 300° C. and a 1 kg/dm³ density at 20°C.

The 199-360° C. fraction is mixed with an extractant (anilide) in a 1:1mass ratio in a mixer. They are mixed thoroughly for one hour at 40° C.After the mixture is cooled, it is drained to a separating funnel whereseparation into two layers takes place. The top layer—the refined199-360° C. fraction—raffinate (85%) and saturated ABT—the extractant(15%)—is separated.

To regenerate the extractant, light gasoline fraction NK-85° C. is addedto the bottom layer with a 1:2 mass ratio of saturated extractant toNK-85° C. fraction. The mixture is mixed for 0.5 hours at 20° C. anddrained to a separating funnel. The bottom layer is separated and usedagain for extraction.

After the extractant is regenerated, the top layer is separated bydistillation into NK-85° C. fraction and a residue (ABT +heavy aromatichydrocarbons). The NK-85° C. fraction is used again to regenerate asaturated extractant, and the separated ABT+heavy aromatic hydrocarbons(15%) are fed to a vacuum gas oil.

Examples 2-6 which demonstrate the results of the claimed invention areshown in Table 1 together with Example 1.

Experiment conditions were changed according to the residual ABT contentin the raffinate—refined diesel fuel.

The mixture of 70-85% of the 171-341° C. fraction and 15-30% of thepurified 199-360° C. fraction, the raffinate (experiments 2-6), is sentfor hydrogen refining on an aluminum-cobalt-molybdenum oraluminum-nickel-molybdenum catalyst. After refining, the amount ofsulfur in diesel fuel is less than 10 ppm.

Industrial Applicability. The proposed method makes it possible toreduce the total sulfur content in straight-run diesel fuel from 1.34%to 0.774% due to reduced ABT content in feedstock for plants forhydrogen refining of diesel fuel using the liquid extraction method. Theproposed method also makes it possible to ensure production of hydrogenrefined diesel fuel with a sulfur content of not more than 10 ppm with awide fractional composition of straight-run diesel fuel.

While hydrogen refining the mixture of 70-85% of the 171-341° C.fraction and 15-30% of the 199-360° C. fraction (without ABT extraction)on an aluminum-cobalt-molybdenum or aluminum-nickel-molybdenum catalyst,the sulfur content of diesel fuel after refining reaches over 50 ppm.

The proposed method makes it possible to produce diesel fuel with asulfur content of not more than 10 ppm, which meets the requirements ofinternational standards. The proposed method also makes it possible toincrease the amount of feedstock for production of diesel fuel bywidening the fractional composition of diesel fuel from EBP 340° C. toEBP 360° C.

The production process of diesel fuel with a sulfur content of not morethan 10 ppm described in the claimed invention can be implemented at oilrefineries and will make it possible to produce diesel fuel with asulfur content of not more than 10 ppm over a wide fractionalcomposition of 170-360° C. diesel fuel.

Parameters of Liquid Extraction and Content of Sulfuric Compounds inFeedstock and Raffinate.

TABLE 1 Raffinate Experiment Number Parameter Feedstock 1 2 3 4 5 6Feedstock:extractant 1:1 1:2 1:2 1:2 1:3 1:4 mass ratio Temperature, °C. 40-45 Time, h 1 2 3 4 3 3 Total sulfur content 1340 0.946 0.844 0.8010.809 0.774 0.785 Mixture of thiophens, 0.01 0.01 0.09 0.0095 0.00910.0092 0.0093 sulfides and mercaptans Benzothiophens and 0.81 0.6240.546 0.507 0.515 0.491 0.499 alkyl-substituted benzothiophensDibenzothiophens 0.52 0.312 0.289 0.285 0.285 0.273 0.277 andalkyl-substituted dibenzothiophens

What is claimed:
 1. A method for production of diesel fuel comprisingoil demineralization and distillation, extraction and mixing of dieselfractions followed by hydrogen refining of a mixture, wherein, duringdistillation in an atmospheric tower, two diesel fractions boiling at171-341° C. and 199-360° C. are extracted, the 199-360° C. fraction issent for liquid extraction to purify said 199-360° C. fraction frombenzalkylthiophens using amide as an extractant, a product of organicamine interaction with organic acid, and the 171-341° C. and 199-360° C.fractions are mixed after refining, and wherein a mixture of thesefractions, when refined using an ASTM D-86 method, has an end boilingpoint no higher than 360° C.
 2. The method of claim 1, wherein theproduced mixture is subject to hydrogen refining on analuminum-cobalt-molybdenum or aluminum-nickel-molybdenum catalyst.